Avionic system of an aircraft

ABSTRACT

The avionic system of an aircraft includes a set of avionic computers and a switch associated with each avionic computer. For each avionic computer of the set of avionic computers, the avionic system includes a communication link between the switch associated with this avionic computer and each of the switches associated with the other avionic computers. Each switch is configured such that it routes the data frames received on its input ports to its output ports in a manner predefined only on the basis of the input ports on which these data frames are received. The various switches are configured such that, when an avionic computer sends a data frame, this data frame is transmitted to all of the other avionic computers.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No.1912834 filed on Nov. 18, 2019, the entire disclosures of which areincorporated herein by way of reference.

FIELD OF THE INVENTION

The invention relates to the field of communications between avioniccomputers of an avionic system of an aircraft. An aircraft has avioniccomputers such as, for example, flight control computers, FMS (flightmanagement system) flight management computers, FWS (flight warningsystem) warning management computers, etc. These avionic computersusually communicate with one another through a communication network ofthe aircraft, this communication network being, for example, inaccordance with the ARINC 664 part 7 standard. Such a communicationnetwork is a deterministic switched Ethernet network using virtual linksthat makes it possible to guarantee the transmission of data framesbetween the computers with a guaranteed latency time. When a switchreceives a data frame on an input port, it analyses this frame in orderto determine the corresponding virtual link, and then it determines theoutput ports on which it should retransmit this data frame, on the basisof a routing table stored in memory. However, in some specificsituations, in particular in the case of an avionic system having alimited number of avionic computers, such as, for example, a flightcontrol system, such a communication network is expensive to implement.Specifically, it requires configuring, in the switches, routing tablescorresponding to the various virtual links. In addition, the mass andthe bulk of the switches increase the cost of the aircraft.

SUMMARY OF THE INVENTION

The present invention aims, in particular, to provide a solution to thisproblem. It relates to an avionic system of an aircraft, the avionicsystem comprising:

-   -   a set of avionic computers; and    -   a switch associated with each avionic computer of the set of        avionic computers, each switch comprising a set of input ports        and a set of output ports.

The avionic system is noteworthy in that, for each avionic computer ofthe set of avionic computers, the avionic system comprises acommunication link between the switch associated with this avioniccomputer and each of the switches associated with the other avioniccomputers of the set of avionic computers,

and in that:

-   -   each switch is configured such that it routes the data frames        received on its input ports to its output ports in a manner        predefined only on the basis of the input ports on which these        data frames are received; and    -   the various switches are configured such that, when an avionic        computer sends a data frame via the switch associated with this        avionic computer, this data frame is transmitted to all of the        other avionic computers of the set of avionic computers.

Routing of the data frames received by a switch is thus simplified incomparison with the prior art, since a data frame received by the switchis routed in a manner predefined only on the basis of the input port onwhich this data frame is received. It is, therefore, not necessary forthe switch to analyze the content of the received data frames in orderto route them. In addition, it is not necessary to configure a routingtable for virtual links in the switch. Although it is simplified, therouting of the data frames is by no means uniform routing. Specifically,the predefined aspect of the routing is different for at least two inputports of a switch. The predefined routing is thus such that, for adifferent first port and second port of the switch, the received framesare routed to at least one third port, different from the first port orfrom the second port, only if these frames are received by the firstport or else (exclusive or) by the second port. For example, if thepredefined routing is such that the frames received by the first portare routed to this third port, then this routing is such that the framesreceived by the second port are not routed to this third port (or viceversa). This does not however rule out there possibly furthermore beinga fourth port for which the received frames, received both by the firstport and by the second port, are routed to this fourth port.

In one embodiment, the switch associated with each avionic computer isintegrated into the avionic computer.

In one particular embodiment, the set of avionic computers comprisespairs of avionic computers such that each pair comprises a firstcomputer acting in control mode and a second computer acting inmonitoring mode monitoring the first computer and, for each pair ofcomputers, the switch associated with the first computer is also theswitch associated with the second computer.

In one embodiment, a maximum bandwidth is allocated to each input portof each switch associated with an avionic computer and the switch isconfigured so as to monitor the reception of data frames on an inputport and to reject received frames if the maximum bandwidth allocated tothis input port is exceeded. In particular, according to a firstalternative, the switch is then configured so as to monitor thereception of data frames on an input port in accordance with a tokenbucket principle. According to a second alternative, the avionic systemis configured so as to allow the transmission of a number N of dataflows via an input port of a switch, N being an integer greater than 1,and the switch is configured so as to monitor the reception of dataframes on an input port in accordance with a token bucket principle byimplementing N token bucket counters, the counter having the highestvalue being decremented when a data frame is received on the input portif this highest value is high enough to authorize the reception of thedata frame.

In one embodiment, the data frames exchanged between the avioniccomputers of the set of avionic computers are of identical sizes,corresponding to a predetermined size. Advantageously, a switchassociated with an avionic computer is configured so as to reject thereception of a data frame on an input port if the size of the data frameis different from the predetermined size.

In one particular embodiment, the data frames exchanged between theavionic computers of the set of avionic computers are in accordance withthe ARINC 664 part 7 standard (or any replacement standard).

Advantageously, all of the switches are configured similarly so as toroute the data frames received on their input ports to their outputports in a manner predefined only on the basis of the input ports onwhich these data frames are received.

In one particular embodiment, the avionic system corresponds to a flightcontrol system of the aircraft and the avionic computers of the set ofavionic computers are flight control computers of the aircraft.

The invention also relates to an aircraft comprising such an avionicsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on reading the followingdescription and on examining the appended figures.

FIG. 1 is a view of an aircraft comprising an avionic system accordingto one embodiment of the invention.

FIG. 2A schematically illustrates an avionic system according to oneembodiment of the invention.

FIG. 2B schematically illustrates an avionic system according to anotherembodiment of the invention.

FIG. 3A illustrates the configuration of a switch of the avionic systemillustrated in FIG. 2A.

FIG. 3B illustrates the configuration of a switch of the avionic systemillustrated in FIG. 2B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The avionic system 10 shown in FIG. 2A comprises a set of avioniccomputers 121 c, 121 m, 122 c, 122 m, 123 c, 123 m, 124 c, 124 m. Theavionic system 10 is, for example, integrated into an avionics bay 2 ofan aircraft 1 as shown in FIG. 1. The avionics bay 2 is, for example,located close to a cockpit 3 of the aircraft. In the particular exampleshown in FIG. 2A, the avionic computers are avionic computers of aflight control system of the aircraft. These computers are then groupedtogether in pairs 121, 122, 123, 124, each pair comprising a firstcomputer 121 c, 122 c, 123 c, 124 c, labelled COM in the figure andacting in control mode. Each pair comprises a second computer 121 m, 122m, 123 m, 124 m, labelled MON in the figure and acting in monitoringmode monitoring the first computer acting in control mode. The controlmode and the monitoring mode are such that, when the pair of computersunder consideration is active, the first computer COM acting in controlmode and the second computer MON acting in monitoring mode bothdetermine similar flight control orders. The orders used to controlactuators of the aircraft are those from the first computer COM actingin control mode. The orders from the second computer MON acting inmonitoring mode are compared to the orders from the first computer COMand, if there is a difference greater than a predetermined thresholdbetween an order from the first computer and a similar order from thesecond computer, the pair of computers is declared to be faulty. Thispair of computers then becomes inactive and another pair of computersbecomes active in its place.

Each avionic computer comprises a processing unit labelled “Proc” in thefigure. This processing unit comprises, for example, a microprocessor ora microcontroller. Each avionic computer also comprises a switch of acommunication network, labelled SW in the figure. In the exampleillustrated in the figure, this switch has 5 bidirectional communicationports, labelled S, C, 1, 2, 3 in the figure. However, another number ofcommunication ports may be contemplated without departing from the scopeof the invention. The communication port S is connected to acommunication port of the processing unit Proc of the avionic computerunder consideration. According to a first alternative, the processingunit Proc and the switch SW of an avionic computer are located on oneand the same electronic board. According to a second alternative, theprocessing unit Proc and the switch SW of an avionic computer arelocated on two separate electronic boards integrated into one and thesame physical housing and supplied with electric power by one and thesame electric power supply.

For each pair 121, 122, 123, 124 of avionic computers, according to onealternative, the first computer COM acting in control mode and thesecond computer MON acting in monitoring mode are integrated intoseparate physical housings. According to another alternative, the firstcomputer COM acting in control mode and the second computer MON actingin monitoring mode are integrated into one and the same physicalhousing.

The switches SW of the two computers COM and MON of one and the samepair of computers are connected to one another by their respective portslabelled C. In the example illustrated in FIG. 2A, the ports 1, 2, 3 ofthe switches SW of the computers COM of each of the pairs of avioniccomputers 121, 122, 123, 124 are connected to ports of the switches SWof the computers COM of the other pairs of avionic computers.

Each switch SW is configured such that it routes the data framesreceived on its input ports to its output ports in a manner predefinedonly on the basis of the input ports on which these data frames arereceived. FIG. 3A illustrates the configuration common to the variousswitches SW of FIG. 2A. FIG. 3A illustrates the routing, to the outputports of a switch, of the data frames received on each of its inputports. A data frame received on the input port S is thus routed to the 4output ports C, 1, 2, 3. A data frame received on the input port C isrouted to the 4 output ports S, 1, 2, 3. A data frame received on anyone of the input ports 1, 2 or 3 is routed to the 2 output ports C andS.

This configuration of the various switches, coupled to theabovementioned set of links between switches, as illustrated in FIG. 2A,makes it possible to establish a communication link between each switchassociated with an avionic computer and each of the switches associatedwith the other avionic computers of the set of avionic computers. Thisconfiguration of the various switches is such that, when an avioniccomputer sends a data frame via the switch associated with this avioniccomputer, this data frame is transmitted to all of the other avioniccomputers of the set of avionic computers. Thus, for example, when theavionic computer 121 c sends a data frame to the switch SW that isassociated therewith, this data frame is received by this switch via itscommunication port S. As indicated above with reference to FIG. 3A, theswitch routes this data frame to its output ports C, 1, 2 and 3. Thedata frame routed to the output port C is received by the input port Cof the switch associated with the computer 121 m, which routes it to itsoutput port S destined for the computer 121 m. The data frame routed tothe output port 1 of the switch associated with the computer 121 c isreceived by the input port 1 of the switch associated with the computer123 c, which routes it firstly to its output port S destined for thecomputer 123 c and secondly to its output port C destined for the switchassociated with the computer 123 m. This switch receives this data frameon its input port C and it routes it to its output port S destined forthe computer 123 m. The data frame routed to the output port 2 of theswitch associated with the computer 121 c is received by the input port1 of the switch associated with the computer 122 c, which routes itfirstly to its output port S destined for the computer 122 c andsecondly to its output port C destined for the switch associated withthe computer 122 m. This switch receives this data frame on its inputport C and it routes it to its output port S destined for the computer122 m. The data frame routed to the output port 3 of the switchassociated with the computer 121 c is received by the input port 1 ofthe switch associated with the computer 124 c, which routes it firstlyto its output port S destined for the computer 124 c and secondly to itsoutput port C destined for the switch associated with the computer 124m. This switch receives this data frame on its input port C and itroutes it to its output port S destined for the computer 124 m. Any dataframe sent by the computer 121 c to the switch SW that is associatedtherewith is thus transmitted to all of the other avionic computers ofthe avionic system 10. Similarly, any data frame sent by any of theother avionic computers 121 m, 122 c, 122 m, 123 c, 123 m, 124 c, 124 mis transmitted to all of the other avionic computers of the avionicsystem 10.

Advantageously, the data frames exchanged between the avionic computersof the set of avionic computers are in accordance with the ARINC 664part 7 standard (version in force as of the filing date of thisapplication, or any replacement standard). Although these data framesuse virtual links, these data frames are not decoded by the switchesassociated with the avionic computers of the avionic system 10. Asindicated above, a data frame sent by an avionic computer of the set ofavionic computers is transmitted to all of the other avionic computersof the set of avionic computers. Upon receiving a data frame, theavionic computers check whether the data frame is intended for them, andthey filter the frames for which they are not the intended recipients.This makes it possible to facilitate the routing of the data frames bythe various switches, since these perform the routing identicallyregardless of their position in the avionic system 10. In addition,these switches do not need to analyze the received data frames to decodethe corresponding virtual links in order to resend these data frames onthe basis of routing tables. The switches are thus simplified. Inaddition, integrating the switches into the avionic computers makes itpossible to simplify the implementation of the avionic system 10.

In one variant embodiment of the avionic system 10 shown in FIG. 2B, theswitches SW associated with the avionic computers each have 5bidirectional communication ports, labelled S, C, G, 1, 2 in the figure.The communication port S of each switch is connected to a communicationport of the processing unit Proc of the avionic computer with which thisswitch is associated. The switches SW of the two computers COM and MONof one and the same pair of computers are connected to one anotherfirstly by their respective ports labelled C, and secondly by theirrespective ports labelled G. In the example illustrated in FIG. 2B,three of the ports 1, 2 of the switches SW of the computers COM and MONof each of the pairs of avionic computers 121, 122, 123, 124 areconnected to ports of the switches SW of the computers COM and MON ofthe other pairs of avionic computers.

Each switch SW is configured such that it routes the data framesreceived on its input ports to its output ports in a manner predefinedonly on the basis of the input ports on which these data frames arereceived. FIG. 3B illustrates the configuration common to the variousswitches SW of FIG. 2B. FIG. 3B illustrates the routing, to the outputports of a switch, of the data frames received on each of its inputports. A data frame received on the input port S is thus routed to the 4output ports C, G, 1, 2. A data frame received on the input port C isrouted to the output port S. A data frame received on the input port Gis routed to the output ports 1 and 2. A data frame received on eitherone of the input ports 1 or 2 is routed to the 2 output ports C and S.

This configuration of the various switches, coupled to theabovementioned set of links between switches, as illustrated in FIG. 2B,makes it possible to establish a communication link between each switchassociated with an avionic computer and each of the switches associatedwith the other avionic computers of the set of avionic computers. Thisconfiguration of the various switches is such that, when an avioniccomputer sends a data frame via the switch associated with this avioniccomputer, this data frame is transmitted to all of the other avioniccomputers of the set of avionic computers, as in the avionic systemillustrated by FIGS. 2A and 3A.

In one particular embodiment not shown in the figures, for each pair ofavionic computers COM and MON, the switch associated with the computerCOM is also the switch associated with the computer MON. This makes itpossible to implement a single switch common to the two computers ofeach pair of computers.

In one advantageous embodiment, a maximum bandwidth is allocated to eachinput port of each switch SW associated with an avionic computer. Thisswitch is then configured so as to monitor the reception of data frameson an input port and to reject received frames if the maximum bandwidthallocated to this input port is exceeded. The maximum bandwidth may becharacterized by a minimum time interval between two consecutive dataframes of a data flow, also called BAG (bandwidth allocation gap). Inparticular, in addition to the BAG, the maximum bandwidth is alsocharacterized by a maximum jitter value. These concepts of BAG andjitter are similar to those used in a communication network inaccordance with the ARINC 664 part 7 standard. In particular, the switchis configured so as to monitor the reception of data frames on an inputport in accordance with a token bucket principle. According to thisprinciple, a counter is incremented in accordance with a predefined timeperiod. When a data frame is received on the input port underconsideration of the switch, if the current value of the counter isgreater than or equal to a predetermined value, the counter isdecremented by the predetermined value. The switch then accepts thereceived data frame. If not, when the current value of the counter isless than this predetermined value, the switch rejects the received dataframe by not retransmitting the data frame on any of its output ports.The predetermined value corresponds to the value of the BAG. Theincrementation of the counter at each time period is subject tosaturation depending on the value of the jitter: for a zero jittervalue, the counter is saturated at the predetermined value correspondingto the BAG. Thus, upon the authorized reception of a data frame, withthe counter being decremented by the predetermined value, its valuereturns to zero. It is then necessary to wait for at least a durationcorresponding to the BAG to be able to accept the reception of a newdata frame, this actually corresponding to the definition of a zerojitter value. For a positive jitter value, the saturation value of thecounter is equal to the predetermined value corresponding to the BAGplus a value corresponding to the jitter. Thus, after the authorizedreception of a data frame, with the counter being decremented by thepredetermined value, its value returns to a value corresponding to thejitter.

In particular, when the avionic system is configured such that an inputport of a switch SW is supposed to receive N data flows, N being aninteger greater than 1, the reception of the data frames on this inputport is monitored by implementing N counters similar to theabovementioned counter corresponding to a token bucket principle. The Ndata flows may, for example, correspond to N virtual links when the dataframes are in accordance with the ARINC 664 part 7 standard. Each of theN counters is incremented at each time period. When a data frame isreceived, one of the N counters, having the highest current value fromamong the current values of the N counters, is taken into consideration.The principle of accepting or declining the received data frame isimplemented on the basis of this counter, similarly to theabovementioned principle implemented with the single counter of aconventional token bucket. Thus, if the current value of this counter isgreater than or equal to a predetermined value, the counter isdecremented by the predetermined value. The switch then accepts thereceived data frame. If not, when the current value of the counter isless than this predetermined value, the switch rejects the received dataframe by not retransmitting the data frame on any of its output ports.Implementing the N counters makes it possible to precisely monitor theBAG and the jitter of the N communication flows able to be received bythe communication port of the switch.

In particular, all of the data frames exchanged between the avioniccomputers of the set of avionic computers are of identical sizes,corresponding to a predetermined size. Advantageously, a switchassociated with an avionic computer is configured so as to reject thereception of a data frame on an input port if the size of the data frameis different from the predetermined size.

As in the case of a communication network in accordance with the ARINC664 part 7 standard, the avionic system according to the invention mayundergo mathematical analysis of the flows on its various communicationlinks in order to determine the maximum end-to-end latencies on thevarious links between the equipment of the avionic system (therebymaking it possible to verify that these latencies are in accordance withthe specifications of the avionic system) and in order to determine aminimum required size for each of the buffers associated with thevarious communication ports. This mathematical analysis also makes itpossible to determine the maximum flows on the various communicationlinks and to accordingly configure the maximum bandwidth allocated toeach input port of each switch.

While at least one exemplary embodiment of the present invention(s) isdisclosed herein, it should be understood that modifications,substitutions and alternatives may be apparent to one of ordinary skillin the art and can be made without departing from the scope of thisdisclosure. This disclosure is intended to cover any adaptations orvariations of the exemplary embodiment(s). In addition, in thisdisclosure, the terms “comprise” or “comprising” do not exclude otherelements or steps, the terms “a” or “one” do not exclude a pluralnumber, and the term “or” means either or both. Furthermore,characteristics or steps which have been described may also be used incombination with other characteristics or steps and in any order unlessthe disclosure or context suggests otherwise. This disclosure herebyincorporates by reference the complete disclosure of any patent orapplication from which it claims benefit or priority.

1. An avionic system of an aircraft, said avionic system comprising: aset of avionic computers; and a switch associated with each avioniccomputer of the set of avionic computers, each switch comprising a setof input ports and a set of output ports; wherein, for each avioniccomputer of the set of avionic computers, the avionic system comprises acommunication link between the switch associated with this avioniccomputer and each of the switches associated with the other avioniccomputers of the set of avionic computers, wherein: each switch isconfigured such that such switch routes data frames received on itsinput ports to its output ports in a manner predefined only based on theinput ports on which these data frames are received; and the variousswitches are configured such that, when an avionic computer sends a dataframe via the switch associated with this avionic computer, this dataframe is transmitted to all of the other avionic computers of the set ofavionic computers.
 2. The avionic system according to claim 1, whereinthe switch associated with each avionic computer is integrated into saidavionic computer.
 3. The avionic system according to claim 1, whereinthe set of avionic computers comprises pairs of avionic computers, suchthat each pair comprises a first computer acting in control mode and asecond computer acting in monitoring mode monitoring the first computerand wherein, for each pair of computers, the switch associated with thefirst computer is also the switch associated with the second computer.4. The avionic system according to claim 1, wherein a maximum bandwidthis allocated to each input port of each switch associated with anavionic computer and said switch is configured to monitor the receptionof data frames on an input port and to reject received frames if themaximum bandwidth allocated to this input port is exceeded.
 5. Theavionic system according to claim 4, wherein the switch is configured tomonitor the reception of data frames on an input port in accordance witha token bucket principle.
 6. The avionic system according to claim 4,wherein the system is configured to allow a transmission of a number Nof data flows via an input port of a switch, N being an integer greaterthan 1, and said switch is configured so as to monitor the reception ofdata frames on an input port in accordance with a token bucket principleby implementing N token bucket counters, a counter of the countershaving a highest value being decremented when a data frame is receivedon the input port if this highest value is high enough to authorize areception of the data frame.
 7. The avionic system according to claim 1,wherein the data frames exchanged between the avionic computers of theset of avionic computers are of identical sizes, corresponding to apredetermined size.
 8. The avionic system according to claim 7, whereina switch associated with an avionic computer is configured to reject areception of a data frame on an input port if the size of said dataframe is different from said predetermined size.
 9. The avionic systemaccording to claim 1, wherein the data frames exchanged between theavionic computers of the set of avionic computers are in accordance withthe ARINC 664 part 7 standard.
 10. The avionic system according to claim1, wherein all of the switches are configured similarly to route thedata frames received on their input ports to their output ports in amanner predefined only based on the input ports on which these dataframes are received.
 11. The avionic system according to claim 1,wherein the system corresponds to a flight control system of theaircraft and the avionic computers of the set of avionic computers areflight control computers of the aircraft.
 12. An aircraft comprising anavionic system according to claim 1.